restructured project (shared-operations)

shared-operations/functions/editMetadata.js

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+/**
+ * @typedef {Object} Metadata
+ * @property {string | null | undefined} Title - The title of the document.
+ * @property {string | null | undefined} Author - The author of the document.
+ * @property {string | null | undefined} Subject - The subject of the document.
+ * @property {string[] | null | undefined} Keywords - An array of keywords associated with the document.
+ * @property {string | null | undefined} Producer - The producer of the document.
+ * @property {string | null | undefined} Creator - The creator of the document.
+ * @property {Date | null | undefined} CreationDate - The date when the document was created.
+ * @property {Date | null | undefined} ModificationDate - The date when the document was last modified.
+ */
+
+/**
+ * 
+ * @param {Uint16Array} snapshot
+ * @param {Metadata} metadata - Set property to null or "" to clear, undefined properties will be skipped.
+ * @param {import('pdf-lib')} PDFLib
+ * @returns 
+ */
+export async function editMetadata(snapshot, metadata, PDFLib) {
+    // Load the original PDF file
+    const pdfDoc = await PDFLib.PDFDocument.load(snapshot, {
+        parseSpeed: PDFLib.ParseSpeeds.Fastest,
+    });
+
+    if(metadata.Title !== undefined)
+        pdfDoc.setTitle(metadata.Title);
+
+    if(metadata.Author !== undefined)
+        pdfDoc.setAuthor(metadata.Author)
+
+    if(metadata.Subject !== undefined)
+        pdfDoc.setSubject(metadata.Subject)
+    
+    if(metadata.Keywords !== undefined)
+        pdfDoc.setKeywords(metadata.Keywords)
+    
+    if(metadata.Producer !== undefined)
+        pdfDoc.setProducer(metadata.Producer)
+
+    if(metadata.Creator !== undefined)
+        pdfDoc.setCreator(metadata.Creator)
+
+    if(metadata.CreationDate !== undefined)
+        pdfDoc.setCreationDate(metadata.CreationDate)
+
+    if(metadata.ModificationDate !== undefined)
+        pdfDoc.setModificationDate(metadata.ModificationDate)
+
+    // Serialize the modified document
+    return pdfDoc.save();
+};

shared-operations/functions/extractPages.js

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+import { createSubDocument } from "./shared/createSubDocument.js";
+
+export async function extractPages(snapshot, pagesToExtractArray, PDFLib) {
+    const pdfDoc = await PDFLib.PDFDocument.load(snapshot)
+
+    // TODO: invent a better format for pagesToExtractArray and convert it.
+    return createSubDocument(pdfDoc, pagesToExtractArray, PDFLib);
+};

shared-operations/functions/impose.js

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+export async function impose(snapshot, nup, format, pdfcpuWraopper) {
+    return await pdfcpuWraopper.oneToOne([
+            "pdfcpu.wasm",
+            "nup",
+            "-c",
+            "disable",
+            'f:' + format,
+            "/output.pdf",
+            String(nup),
+            "input.pdf",
+        ], snapshot);
+}

shared-operations/functions/mergePDFs.js

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+export const mergePDFs = async (snapshots, PDFLib) => {
+
+    const mergedPdf = await PDFLib.PDFDocument.create(); 
+
+    for (let i = 0; i < snapshots.length; i++) {
+        const pdfToMerge = await PDFLib.PDFDocument.load(snapshots[i]);
+
+        const copiedPages = await mergedPdf.copyPages(pdfToMerge, pdfToMerge.getPageIndices());
+        copiedPages.forEach((page) => mergedPdf.addPage(page));
+    }
+
+    return mergedPdf.save();
+};

shared-operations/functions/organizePages.js

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+/**
+ * @typedef {"CUSTOM_PAGE_ORDER"|"REVERSE_ORDER"|"DUPLEX_SORT"|"BOOKLET_SORT"|"ODD_EVEN_SPLIT"|"REMOVE_FIRST"|"REMOVE_LAST"|"REMOVE_FIRST_AND_LAST"} OrderOperation
+ */
+
+/**
+ * 
+ * @param {Uint16Array} snapshot
+ * @param {OrderOperation} operation
+ * @param {string} customOrderString
+ * @param {import('pdf-lib')} PDFLib
+ * @returns 
+ */
+export async function organizePages(snapshot, operation, customOrderString, PDFLib) {
+    const pdfDoc = await PDFLib.PDFDocument.load(snapshot);
+    let subDocument = await PDFLib.PDFDocument.create();
+    const copiedPages = await subDocument.copyPages(pdfDoc, pdfDoc.getPageIndices());
+
+
+    const pageCount = pdfDoc.getPages().length;
+
+    switch (operation) {
+        case "CUSTOM_PAGE_ORDER":
+            console.log("Custom Order");
+            const pageOrderArray = parseCustomPageOrder(customOrderString, pageCount);
+            console.log(pageOrderArray);
+
+            const customOrderedPages = pageOrderArray.map((pageIndex) => copiedPages[pageIndex]);
+            customOrderedPages.forEach((page) => subDocument.addPage(page));
+            break;
+        case "REVERSE_ORDER":
+            const reversedPages = [];
+            for (let i = pageCount - 1; i >= 0; i--) {
+                reversedPages.push(copiedPages[i]);
+            }
+            reversedPages.forEach((page) => subDocument.addPage(page));
+            break;
+        case 'DUPLEX_SORT': //TODO: Needs to be checked by someone who knows more about duplex printing.
+            const duplexPages = [];
+            const half = (pageCount + 1) / 2
+            for (let i = 1; i <= half; i++) {
+                duplexPages.push(copiedPages[i - 1]);
+                if (i <= pageCount - half) {
+                    duplexPages.push(copiedPages[pageCount - i]);
+                }
+            }
+            duplexPages.forEach((page) => subDocument.addPage(page));
+            break;
+        case 'BOOKLET_SORT':
+            const bookletPages = [];
+            for (let i = 0; i < pageCount / 2; i++) {
+                bookletPages.push(copiedPages[i]);
+                bookletPages.push(copiedPages[pageCount - i - 1]);
+            }
+            bookletPages.forEach((page) => subDocument.addPage(page));
+            break;
+        case 'ODD_EVEN_SPLIT':
+            const oddPages = [];
+            const evenPages = [];
+            for (let i = 0; i < pageCount; i++) {
+                if (i % 2 === 0) {
+                    evenPages.push(copiedPages[i]);
+                } else {
+                    oddPages.push(copiedPages[i]);
+                }
+            }
+            oddPages.forEach((page) => subDocument.addPage(page));
+            evenPages.forEach((page) => subDocument.addPage(page));
+            break;
+        case 'REMOVE_FIRST':
+            pdfDoc.removePage(0);
+            subDocument = pdfDoc;
+            break;
+        case 'REMOVE_LAST':
+            pdfDoc.removePage(pageCount - 1);
+            subDocument = pdfDoc;
+            break;
+        case 'REMOVE_FIRST_AND_LAST':
+            pdfDoc.removePage(0);
+            pdfDoc.removePage(pageCount - 2);
+            subDocument = pdfDoc;
+            break;
+        default:
+            throw new Error("Operation not supported");
+            break;
+    }
+
+    return subDocument.save();
+};
+
+function parseCustomPageOrder(customOrder, pageCount) {
+    const pageOrderArray = [];
+    const ranges = customOrder.split(',');
+
+    ranges.forEach((range) => {
+        if (range.includes('-')) {
+            const [start, end] = range.split('-').map(Number);
+            for (let i = start; i <= end; i++) {
+                pageOrderArray.push(i - 1);
+            }
+        } else if (range.includes('n')) {
+            const [even, odd] = range.split('n').map(Number);
+            for (let i = 1; i <= pageCount; i++) {
+                if (i % 2 === 0) {
+                    pageOrderArray.push((i * even) - 1);
+                } else {
+                    pageOrderArray.push((i * odd) - 1);
+                }
+            }
+        } else {
+            pageOrderArray.push(Number(range) - 1);
+        }
+    });
+
+    return pageOrderArray;
+}

shared-operations/functions/removeBlankPages.js

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+import { detectEmptyPages } from "./shared/detectEmptyPages.js";
+
+export async function removeBlankPages(snapshot, whiteThreashold, PDFJS, OpenCV, PDFLib) {
+    
+    const emptyPages = await detectEmptyPages(snapshot, whiteThreashold, PDFJS, OpenCV);
+
+    console.log("Empty Pages: ", emptyPages);
+
+    const pdfDoc = await PDFLib.PDFDocument.load(snapshot);
+
+    // Reverse the array before looping in order to keep the indecies at the right pages. E.g. if you delete page 5 page 7 becomes page 6, if you delete page 7 page 5 remains page 5
+    emptyPages.reverse().forEach(pageIndex => {
+        pdfDoc.removePage(pageIndex);
+    })
+
+    return pdfDoc.save();
+};

shared-operations/functions/rotatePages.js

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+export async function rotatePages (snapshot, rotation, PDFLib) {
+    // Load the original PDF file
+    const pdfDoc = await PDFLib.PDFDocument.load(snapshot, {
+        parseSpeed: PDFLib.ParseSpeeds.Fastest,
+    });
+
+    const pages = pdfDoc.getPages();
+
+    pages.forEach(page => {
+        // Change page size
+        page.setRotation(PDFLib.degrees(rotation))
+    });
+
+    // Serialize the modified document
+    return pdfDoc.save();
+};

shared-operations/functions/scaleContent.js

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+export async function scaleContent(snapshot, scaleFactor, PDFLib) {
+    // Load the original PDF file
+    const pdfDoc = await PDFLib.PDFDocument.load(snapshot, {
+        parseSpeed: PDFLib.ParseSpeeds.Fastest,
+    });
+
+    const pages = pdfDoc.getPages();
+
+    pages.forEach(page => {
+        const width = page.getWidth();
+        const height = page.getHeight();
+        
+        // Scale content
+        page.scaleContent(scaleFactor, scaleFactor);
+        const scaled_diff = {
+            width: Math.round(width - scaleFactor * width),
+            height: Math.round(height - scaleFactor * height),
+        };
+
+        // Center content in new page format
+        page.translateContent(Math.round(scaled_diff.width / 2), Math.round(scaled_diff.height / 2));
+
+    });
+
+    // Serialize the modified document
+    return pdfDoc.save();
+};

shared-operations/functions/scalePage.js

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+export async function scalePage(snapshot, pageSize, PDFLib) {
+    // Load the original PDF file
+    const pdfDoc = await PDFLib.PDFDocument.load(snapshot, {
+        parseSpeed: PDFLib.ParseSpeeds.Fastest,
+    });
+
+    const new_size = pageSize;
+
+    const pages = pdfDoc.getPages();
+
+    pages.forEach(page => {
+        // Change page size
+        page.setSize(new_size.width, new_size.height);
+    });
+
+    // Serialize the modified document
+    return pdfDoc.save();
+};
+
+export const PageSize = {
+    a4: {
+        width: 594.96,
+        height: 841.92
+    },
+    letter: {
+        width: 612,
+        height: 792
+    }
+};

shared-operations/functions/shared/createSubDocument.js

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+export async function createSubDocument(pdfDoc, pagesToExtractArray, PDFLib) {
+    const subDocument = await PDFLib.PDFDocument.create();
+
+    // Check that array max number is not larger pdf pages number
+    if(Math.max(...pagesToExtractArray) >= pdfDoc.getPageCount()) {
+        throw new Error(`The PDF document only has ${pdfDoc.getPageCount()} pages and you tried to extract page ${Math.max(...pagesToExtractArray)}`);
+    }
+
+    const copiedPages = await subDocument.copyPages(pdfDoc, pagesToExtractArray);
+
+    for (let i = 0; i < copiedPages.length; i++) {
+        subDocument.addPage(copiedPages[i]);
+    }
+
+    return subDocument.save();
+}

shared-operations/functions/shared/detectEmptyPages.js

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+import { getImagesOnPage } from "./getImagesOnPage.js";
+
+export async function detectEmptyPages(snapshot, whiteThreashold, PDFJS, OpenCV) {
+    const pdfDoc = await PDFJS.getDocument(snapshot).promise;
+
+    const emptyPages = [];
+    for (let i = 1; i <= pdfDoc.numPages; i++) {
+        const page = await pdfDoc.getPage(i);
+        console.log("Checking page " + i);
+
+        if(!await hasText(page)) {
+            console.log(`Found text on Page ${i}, page is not empty`);
+            continue;
+        }
+
+        if(!await areImagesBlank(page, whiteThreashold)) {
+            console.log(`Found non white image on Page ${i}, page is not empty`);
+            continue;
+        }
+
+        console.log(`Page ${i} is empty.`);
+        emptyPages.push(i - 1);
+    }
+    return emptyPages;
+
+    async function hasText(page) {
+        const textContent = await page.getTextContent();
+        return textContent.items.length === 0;
+    }
+
+    async function areImagesBlank(page, threshold) {
+        const images = await getImagesOnPage(page, PDFJS);
+        for (const image of images) {
+            if(!isImageBlank(image, threshold))
+                return false;
+        }
+        return true;
+    }
+    
+    function isImageBlank(image, threshold) {
+        const src = new OpenCV.cv.Mat(image.width, image.height, OpenCV.cv.CV_8UC4);
+        src.data.set(image.data);
+        // Convert the image to grayscale
+        const gray = new OpenCV.cv.Mat();
+        OpenCV.cv.cvtColor(src, gray, OpenCV.cv.COLOR_RGBA2GRAY);
+    
+        // Calculate the mean value of the grayscale image
+        const meanValue = OpenCV.cv.mean(gray);
+    
+        // Free memory
+        src.delete();
+        gray.delete();
+    
+        // Check if the mean value is below the threshold
+        if (meanValue[0] <= threshold) {
+            return true;
+        } else {
+            return false;
+        }
+    }
+}

shared-operations/functions/shared/getImagesOnPage.js

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+export async function getImagesOnPage(page, PDFJS) {
+    const ops = await page.getOperatorList();
+    const images = [];
+    for (var j=0; j < ops.fnArray.length; j++) {
+        if (ops.fnArray[j] == PDFJS.OPS.paintJpegXObject || ops.fnArray[j] == PDFJS.OPS.paintImageXObject) {
+            const image = page.objs.get(ops.argsArray[j][0]);
+            images.push(image);
+        }
+    }
+    return images;
+}

shared-operations/functions/splitOn.js

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+import { detectEmptyPages } from "./shared/detectEmptyPages.js";
+import { getImagesOnPage } from "./shared/getImagesOnPage.js";
+import { createSubDocument } from "./shared/createSubDocument.js";
+
+/**
+ * @typedef {"BAR_CODE"|"QR_CODE"|"BLANK_PAGE"} SplitType
+ */
+
+/**
+ * 
+ * @param {Uint16Array} snapshot
+ * @param {SplitType} type
+ * @param {} PDFJS
+ * @param {import('opencv-wasm')} OpenCV
+ * @param {} PDFLib
+ * @returns 
+ */
+export async function splitOn(snapshot, type, whiteThreashold, PDFJS, OpenCV, PDFLib, jsQR) {
+    
+    let splitAtPages = [];
+
+    switch (type) {
+        case "BAR_CODE":
+            // TODO: Implement
+            throw new Error("This split-type has not been implemented yet");
+            break;
+
+        case "QR_CODE":
+            splitAtPages = await getPagesWithQRCode(snapshot);
+            break;
+
+        case "BLANK_PAGE":
+            splitAtPages = await detectEmptyPages(snapshot, whiteThreashold, PDFJS, OpenCV);
+            break;
+    
+        default:
+            throw new Error("An invalid split-type was provided.")
+            break;
+    }
+
+    console.log("Split At Pages: ", splitAtPages);
+
+    // Remove detected Pages & Split
+    const pdfDoc = await PDFLib.PDFDocument.load(snapshot);
+
+    const numberOfPages = pdfDoc.getPages().length;
+
+    let pagesArray = [];
+    let splitAfter = splitAtPages.shift();
+    const subDocuments = [];
+
+    for (let i = 0; i < numberOfPages; i++) {
+        console.log(i);
+        if(i == splitAfter) {
+            if(pagesArray.length > 0) {
+                subDocuments.push(await createSubDocument(pdfDoc, pagesArray, PDFLib));
+                pagesArray = [];
+            }
+            splitAfter = splitAtPages.shift();
+        }
+        else { // Skip splitAtPage
+            console.log("PagesArray")
+            pagesArray.push(i);
+        }
+    }
+    if(pagesArray.length > 0) {
+        subDocuments.push(await createSubDocument(pdfDoc, pagesArray, PDFLib)); 
+    }
+    pagesArray = [];
+
+    return subDocuments;
+
+    async function getPagesWithQRCode(snapshot) {
+        const pdfDoc = await PDFJS.getDocument(snapshot).promise;
+
+        const pagesWithQR = [];
+        for (let i = 0; i < pdfDoc.numPages; i++) {
+            console.log("Page:", i, "/", pdfDoc.numPages);
+            const page = await pdfDoc.getPage(i + 1);
+
+            const images = await getImagesOnPage(page, PDFJS);
+            console.log("images:", images);
+            for (const image of images) {
+                const data = await checkForQROnImage(image);
+                if(data == "https://github.com/Frooodle/Stirling-PDF") {
+                    pagesWithQR.push(i);
+                }
+            }
+        }
+        if(pagesWithQR.length == 0) {
+            console.warn("Could not find any QR Codes in the provided PDF.")
+        }
+        return pagesWithQR;
+    }
+
+    async function checkForQROnImage(image) {
+        // TODO: There is an issue with the jsQR package (The package expects rgba but sometimes we have rgb), and the package seems to be stale, we could create a fork and fix the issue. In the meanwhile we just force rgba:
+        // Check for rgb and convert to rgba
+
+        if(image.data.length == image.width * image.height * 3) {
+            const tmpArray = new Uint8ClampedArray(image.width * image.height * 4);
+
+            // Iterate through the original array and add an alpha channel
+            for (let i = 0, j = 0; i < image.data.length; i += 3, j += 4) {
+                tmpArray[j] = image.data[i];     // Red channel
+                tmpArray[j + 1] = image.data[i + 1]; // Green channel
+                tmpArray[j + 2] = image.data[i + 2]; // Blue channel
+                tmpArray[j + 3] = 255;               // Alpha channel (fully opaque)
+            }
+
+            image.data = tmpArray;
+        }
+
+        const code = jsQR(image.data, image.width, image.height);
+        if(code)
+            return code.data;
+        else
+            return null;
+    }
+};

shared-operations/functions/splitPDF.js

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+import { createSubDocument } from "./shared/createSubDocument.js";
+
+export async function splitPDF(snapshot, splitAfterPageArray, PDFLib) {
+    const pdfDoc = await PDFLib.PDFDocument.load(snapshot)
+
+    const numberOfPages = pdfDoc.getPages().length;
+
+    let pagesArray = [];
+    let splitAfter = splitAfterPageArray.shift();
+    const subDocuments = [];
+
+    for (let i = 0; i < numberOfPages; i++) {
+        if(i > splitAfter && pagesArray.length > 0) {
+            subDocuments.push(await createSubDocument(pdfDoc, pagesArray, PDFLib));
+            splitAfter = splitAfterPageArray.shift();
+            pagesArray = [];
+        }
+        pagesArray.push(i);        
+    }
+    subDocuments.push(await createSubDocument(pdfDoc, pagesArray, PDFLib));
+    pagesArray = [];
+
+    return subDocuments;
+};

shared-operations/organizeWaitOperations.js

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+
+export function organizeWaitOperations(operations) {
+
+    // Initialize an object to store the counts and associated "done" operations
+    const waitCounts = {};
+    const doneOperations = {};
+
+    // Function to count "type: wait" operations and associate "done" operations per id
+    function countWaitOperationsAndDone(operations) {
+        for (const operation of operations) {
+            if (operation.type === "wait") {
+                const id = operation.values.id;
+                if (id in waitCounts) {
+                    waitCounts[id]++;
+                } else {
+                    waitCounts[id] = 1;
+                }
+            }
+            if (operation.type === "done") {
+                const id = operation.values.id;
+                doneOperations[id] = operation;
+            }
+            if (operation.operations) {
+                countWaitOperationsAndDone(operation.operations);
+            }
+        }
+    }
+
+    // Start counting and associating from the root operations
+    countWaitOperationsAndDone(operations);
+
+    // Combine counts and associated "done" operations
+    const result = {};
+    for (const id in waitCounts) {
+        result[id] = {
+            waitCount: waitCounts[id],
+            doneOperation: doneOperations[id],
+            input: []
+        };
+    }
+    return result;
+}
+

shared-operations/traverseOperations.js

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+import { organizeWaitOperations } from "./organizeWaitOperations.js";
+
+/**
+ * @typedef PDF
+ * @property {string} originalFileName
+ * @property {string} fileName
+ * @property {Uint8Array} buffer
+ */
+
+/**
+ * 
+ * @param {JSON} operations 
+ * @param {PDF|PDF[]} input 
+ * @param {import('./functions.js')} Functions 
+ * @returns {}
+ */
+export async function * traverseOperations(operations, input, Functions) {
+    const waitOperations = organizeWaitOperations(operations);
+    /** @type {PDF[]} */ let results = [];
+    yield* nextOperation(operations, input);
+    return results;
+
+    /**
+     * 
+     * @param {JSON} operations 
+     * @param {PDF|PDF[]} input 
+     * @returns {undefined}
+     */
+    async function * nextOperation(operations, input) {
+        if(Array.isArray(operations) && operations.length == 0) { // isEmpty
+            if(Array.isArray(input)) {
+                console.log("operation done: " + input[0].fileName + input.length > 1 ? "+" : "");
+                results = results.concat(input);
+                return;
+            }
+            else {
+                console.log("operation done: " + input.fileName);
+                results.push(input);
+                return;
+            }
+        }
+    
+        for (let i = 0; i < operations.length; i++) {
+            yield* computeOperation(operations[i], structuredClone(input));
+        }
+    }
+    
+    /**
+     * 
+     * @param {JSON} operation
+     * @param {PDF|PDF[]} input 
+     * @returns {undefined}
+     */
+    async function * computeOperation(operation, input) {
+        yield "Starting: " + operation.type;
+        switch (operation.type) {
+            case "done": // Skip this, because it is a valid node.
+                break;
+            case "wait":
+                const waitOperation = waitOperations[operation.values.id];
+
+                if(Array.isArray(input)) {
+                    waitOperation.input.concat(input); // TODO: May have unexpected concequences. Needs further testing!
+                }
+                else {
+                    waitOperation.input.push(input);
+                }
+
+                waitOperation.waitCount--;
+                if(waitOperation.waitCount == 0) {
+                    yield* nextOperation(waitOperation.doneOperation.operations, waitOperation.input);
+                }
+                break;
+            case "extract":
+                yield* nToN(input, operation, async (input) => {
+                    input.fileName += "_extractedPages";
+                    input.buffer = await Functions.extractPages(input.buffer, operation.values["pagesToExtractArray"]);
+                });
+                break;
+            case "impose":
+                yield* nToN(input, operation, async (input) => {
+                    input.fileName += "_imposed";
+                    input.buffer = await Functions.impose(input.buffer, operation.values["nup"], operation.values["format"]);
+                });
+                break;
+            case "merge":
+                yield* nToOne(input, operation, async (inputs) => {
+                    return {
+                        originalFileName: inputs.map(input => input.originalFileName).join("_and_"),
+                        fileName: inputs.map(input => input.fileName).join("_and_") + "_merged",
+                        buffer: await Functions.mergePDFs(inputs.map(input => input.buffer))
+                    }
+                });
+                break;
+            case "rotate":
+                yield* nToN(input, operation, async (input) => {
+                    input.fileName += "_turned";
+                    input.buffer = await Functions.rotatePages(input.buffer, operation.values["rotation"]);
+                });
+                break;
+            case "split":
+                // TODO: A split might break the done condition, it may count multiple times. Needs further testing!
+                yield* oneToN(input, operation, async (input) => {
+                    const splitResult = await Functions.splitPDF(input.buffer, operation.values["pagesToSplitAfterArray"]);
+    
+                    const splits = [];
+                    for (let j = 0; j < splitResult.length; j++) {
+                        splits.push({
+                            originalFileName: input.originalFileName,
+                            fileName: input.fileName + "_split" + j,
+                            buffer: splitResult[j]
+                        })
+                    }
+                    return splits;
+                });
+                break;
+            case "editMetadata":
+                yield* nToN(input, operation, async (input) => {
+                    input.fileName += "_metadataEdited";
+                    input.buffer = await Functions.editMetadata(input.buffer, operation.values["metadata"]);
+                });
+                break;
+            case "organizePages":
+                yield* nToN(input, operation, async (input) => {
+                    input.fileName += "_pagesOrganized";
+                    input.buffer = await Functions.organizePages(input.buffer, operation.values["operation"], operation.values["customOrderString"]);
+                });
+                break;
+            case "removeBlankPages":
+                yield* nToN(input, operation, async (input) => {
+                    input.fileName += "_removedBlanks";
+                    input.buffer = await Functions.removeBlankPages(input.buffer, operation.values["whiteThreashold"]);
+                });
+                break;
+            case "splitOn":
+                yield* oneToN(input, operation, async (input) => {
+                    const splitResult = await Functions.splitOn(input.buffer, operation.values["type"], operation.values["whiteThreashold"]);
+                    const splits = [];
+                    for (let j = 0; j < splitResult.length; j++) {
+                        splits.push({
+                            originalFileName: input.originalFileName,
+                            fileName: input.fileName + "_split" + j,
+                            buffer: splitResult[j]
+                        })
+                    }
+    
+                    return splits;
+                });
+                break;
+            default:
+                throw new Error(`${operation.type} not implemented yet.`);
+                break;
+        }
+    }
+
+    /**
+     * 
+     * @param {PDF|PDF[]} input 
+     * @param {JSON} operation
+     * @returns {undefined}
+     */
+    async function * nToOne(inputs, operation, callback) {
+        inputs = Array.from(inputs); // Convert single values to array, keep arrays as is.
+        
+        inputs = await callback(inputs);
+        yield* nextOperation(operation.operations, inputs);
+    }
+
+    /**
+     * 
+     * @param {PDF|PDF[]} input 
+     * @param {JSON} operation
+     * @returns {undefined}
+     */
+    async function * oneToN(input, operation, callback) {
+        if(Array.isArray(input)) {
+            let output = [];
+            for (let i = 0; i < input.length; i++) {
+                output = output.concat(await callback(input[i]));
+            }
+            yield* nextOperation(operation.operations, output);
+        }
+        else {
+            input = await callback(input);
+            yield* nextOperation(operation.operations, input);
+        }
+    }
+
+    /**
+     * 
+     * @param {PDF|PDF[]} input 
+     * @param {JSON} operation
+     * @returns {undefined}
+     */
+    async function * nToN(input, operation, callback) {
+        if(Array.isArray(input)) {
+            for (let i = 0; i < input.length; i++) {
+                await callback(input[i]);
+            }
+            yield* nextOperation(operation.operations, input);
+        }
+        else {
+            await callback(input);
+            yield* nextOperation(operation.operations, input);
+        }
+    }
+}

shared-operations/wasm/pdfcpu/pdfcpu-wrapper-browser.js

@@ -0,0 +1,104 @@
+// imports browserfs via index.html script-tag
+
+let wasmLocation = "/wasm/pdfcpu/";
+
+let fs;
+let Buffer;
+
+// TODO: This can later be defered to load asynchronously
+configureFs();
+loadWasm();
+
+function configureFs() {
+    BrowserFS.configure(
+        {
+            fs: "InMemory",
+        },
+        function (e) {
+            if (e) {
+                // An error happened!
+                throw e;
+            }
+            fs = BrowserFS.BFSRequire("fs");
+            Buffer = BrowserFS.BFSRequire("buffer").Buffer;
+
+            window.fs = fs;
+            window.Buffer = Buffer;
+        }
+    );
+}
+
+function loadWasm() {
+    const script = document.createElement("script");
+    script.src = wasmLocation + "/wasm_exec.js";
+    script.async = true;
+    document.body.appendChild(script);
+}
+
+const runWasm = async (param) => {
+    if (window.cachedWasmResponse === undefined) {
+        const response = await fetch(wasmLocation + "/pdfcpu.wasm");
+        const buffer = await response.arrayBuffer();
+        window.cachedWasmResponse = buffer;
+        window.go = new Go();
+    }
+    const { instance } = await WebAssembly.instantiate(
+        window.cachedWasmResponse,
+        window.go.importObject
+    );
+    window.go.argv = param;
+    await window.go.run(instance);
+    return window.go.exitCode;
+};
+
+async function loadFileAsync(data) {
+    console.log(`Writing file to MemoryFS`);
+    await fs.writeFile(`/input.pdf`, data);
+    console.log(`Write done. Validating...`);
+    let exitcode = await runWasm([
+        "pdfcpu.wasm",
+        "validate",
+        "-c",
+        "disable",
+        `/input.pdf`,
+    ]);
+
+    if (exitcode !== 0)
+        throw new Error("There was an error validating your PDFs");
+
+    console.log(`File is Valid`);
+}
+
+export async function impose(snapshot, nup, format) {
+    
+};
+
+export async function oneToOne(wasmArray, snapshot) {
+    await loadFileAsync(Buffer.from(snapshot));
+
+    console.log("Nuping File");
+    let exitcode = await runWasm(wasmArray);
+
+    if (exitcode !== 0) {
+        console.error("There was an error nuping your PDFs");
+        return;
+    }
+
+    await fs.unlink("input.pdf");
+    const contents = fs.readFileSync("output.pdf");
+    fs.unlink("output.pdf");
+    console.log("Your File ist Ready!");
+    return new Uint8Array(contents);
+}
+
+export async function manyToOne() {
+    //TODO: Do this of neccesary for some operations
+}
+
+export async function oneToMany() {
+    //TODO: Do this of neccesary for some operations
+}
+
+export async function manyToMany() {
+    //TODO: Do this of neccesary for some operations
+}

shared-operations/wasm/pdfcpu/pdfcpu-wrapper-node.js

@@ -0,0 +1,145 @@
+import { WasmFs } from '@wasmer/wasmfs';
+import path from "path";
+
+let webWasmLocation = "/wasm/";
+let nodeWasmLocation = "./public/wasm/";
+
+let fs;
+const wasmfs = new WasmFs();
+
+// TODO: This can later be defered to load asynchronously
+(async () => {
+    await loadWasm();
+    await configureFs();
+})();
+
+async function configureFs() {
+    // Can't use BrowserFS: https://github.com/jvilk/BrowserFS/issues/271
+    fs = wasmfs.fs; 
+    global.fs = fs;
+
+    console.log("InMemoryFs configured");
+}
+
+async function loadWasm() {
+    global.crypto = (await import("crypto")).webcrypto; // wasm dependecy
+    await import("./wasm_exec.js");
+}
+
+const runWasm = async (param) => {
+    if (global.cachedWasmResponse === undefined) {
+        const buffer = (await import("fs")).readFileSync(nodeWasmLocation + "/pdfcpu.wasm");
+        global.cachedWasmResponse = buffer;
+        global.go = new Go();
+    }
+    const { instance } = await WebAssembly.instantiate(
+        global.cachedWasmResponse,
+        global.go.importObject
+    );
+    global.go.argv = param;
+    await global.go.run(instance);
+    return global.go.exitCode;
+};
+
+async function loadFileAsync(data) {
+    console.log(`Writing file to Disk`);
+    fs.writeFileSync(`input.pdf`, data);
+    console.log(`Write done. Validating...`);
+    let exitcode = await runWasm([
+        "pdfcpu.wasm",
+        "validate",
+        "-c",
+        "disable",
+        `input.pdf`,
+    ]);
+    if (exitcode !== 0)
+        throw new Error("There was an error validating your PDFs");
+
+    // // Get logs of command
+    // wasmfs.getStdOut().then(response => {
+    //     console.log(response);
+    // });
+    
+    console.log(`File is Valid`);
+}
+
+export async function oneToOne(wasmArray, snapshot) {
+    await loadFileAsync(Buffer.from(snapshot));
+
+    console.log("Nuping File");
+
+    let exitcode = await runWasm(wasmArray);
+    if (exitcode !== 0) {
+        console.error("There was an error nuping your PDFs");
+        return;
+    }
+    console.log("Nuping Done");
+    
+    await checkExistsWithTimeout("/output.pdf", 1000);
+    console.log("Write started...");
+
+
+    // TODO: Make this more elegant, this waits for the write to finish.
+    // Maybe replace wasmfs with https://github.com/streamich/memfs
+    let fileSize;
+    while (true) {
+        fileSize = fs.statSync("/output.pdf").size;
+        await new Promise((resolve, reject) => {
+            setTimeout(() => {
+                resolve();
+            }, 50);
+        });
+        if(fileSize > 0 && fileSize == fs.statSync("/output.pdf").size) // Wait for file Size not changing anymore.
+            break;
+    }
+    
+    console.log("Could be done?");
+
+    fs.unlinkSync("input.pdf");
+
+    const data = fs.readFileSync("/output.pdf"); 
+    if(data.length == 0) {
+        throw Error("File Size 0 that should not happen. The write probably didn't finish in time.");
+    }
+    fs.unlinkSync("output.pdf");
+    console.log("Your File ist Ready!");
+    return new Uint8Array(data);
+}
+
+export async function manyToOne() {
+    //TODO: Do this if necessary for some pdfcpu operations
+}
+
+export async function oneToMany() {
+    //TODO: Do this if necessary for some pdfcpu operations
+}
+
+export async function manyToMany() {
+    //TODO: Do this if necessary for some pdfcpu operations
+}
+
+// THX: https://stackoverflow.com/questions/26165725/nodejs-check-file-exists-if-not-wait-till-it-exist
+function checkExistsWithTimeout(filePath, timeout) {
+    return new Promise(function (resolve, reject) {
+
+        var timer = setTimeout(function () {
+            watcher.close();
+            reject(new Error('File did not exists and was not created during the timeout.'));
+        }, timeout);
+
+        fs.access(filePath, fs.constants.R_OK, function (err) {
+            if (!err) {
+                clearTimeout(timer);
+                watcher.close();
+                resolve();
+            }
+        });
+
+        var dir = path.dirname(filePath);
+        var watcher = fs.watch(dir, function (eventType, filename) {
+            clearTimeout(timer);
+            watcher.close();
+            resolve();
+        });
+    });
+}

shared-operations/wasm/pdfcpu/wasm_exec.js

@@ -0,0 +1,872 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+(() => {
+	// Map multiple JavaScript environments to a single common API,
+	// preferring web standards over Node.js API.
+	//
+	// Environments considered:
+	// - Browsers
+	// - Node.js
+	// - Electron
+	// - Parcel
+	// - Webpack
+
+	console.log("imported")
+	if (typeof global !== "undefined") {
+		// global already exists
+	} else if (typeof window !== "undefined") {
+		window.global = window;
+	} else if (typeof self !== "undefined") {
+		self.global = self;
+	} else {
+		throw new Error("cannot export Go (neither global, window nor self is defined)");
+	}
+
+	let logFS = false
+	var handler = {
+		get: function (target, property) {
+			if (property in target && target[property] instanceof Function) {
+				return function () {
+					if (logFS) {
+						console.log(property, 'called', arguments);
+					}
+					// 将callback替换
+					if (arguments[arguments.length - 1] instanceof Function) {
+						var origCB = arguments[arguments.length - 1];
+						var newCB = function () {
+							if (logFS) {
+								console.log('callback for', property, 'get called with args:', arguments);
+							}
+							return Reflect.apply(origCB, arguments.callee, arguments);
+						}
+						arguments[arguments.length - 1] = newCB;
+					}
+					return Reflect.apply(target[property], target, arguments);
+				}
+			} else {
+				return target[property]
+			}
+		}
+	}
+
+	if (!global.require && typeof require !== "undefined") {
+		global.require = require;
+	}
+
+
+	if (!global.fs && global.require) {
+
+		//const fs = require("fs");
+		if (typeof fs === "object" && fs !== null && Object.keys(fs).length !== 0) {
+			global.fs = fs;
+		}
+
+	}
+
+	const enosys = () => {
+		const err = new Error("not implemented");
+		err.code = "ENOSYS";
+		return err;
+	};
+
+	if (!global.fs) {
+		let outputBuf = "";
+		global.fs = {
+			constants: {
+				O_WRONLY: -1,
+				O_RDWR: -1,
+				O_CREAT: -1,
+				O_TRUNC: -1,
+				O_APPEND: -1,
+				O_EXCL: -1
+			}, // unused
+			writeSync(fd, buf) {
+				outputBuf += decoder.decode(buf);
+				const nl = outputBuf.lastIndexOf("\n");
+				if (nl != -1) {
+					console.log(outputBuf.substr(0, nl));
+					outputBuf = outputBuf.substr(nl + 1);
+				}
+				return buf.length;
+			},
+			write(fd, buf, offset, length, position, callback) {
+				if (offset !== 0 || length !== buf.length || position !== null) {
+					callback(enosys());
+					return;
+				}
+				const n = this.writeSync(fd, buf);
+				callback(null, n);
+			},
+			chmod(path, mode, callback) {
+				callback(enosys());
+			},
+			chown(path, uid, gid, callback) {
+				callback(enosys());
+			},
+			close(fd, callback) {
+				callback(enosys());
+			},
+			fchmod(fd, mode, callback) {
+				callback(enosys());
+			},
+			fchown(fd, uid, gid, callback) {
+				callback(enosys());
+			},
+			fstat(fd, callback) {
+				callback(enosys());
+			},
+			fsync(fd, callback) {
+				callback(null);
+			},
+			ftruncate(fd, length, callback) {
+				callback(enosys());
+			},
+			lchown(path, uid, gid, callback) {
+				callback(enosys());
+			},
+			link(path, link, callback) {
+				callback(enosys());
+			},
+			lstat(path, callback) {
+				callback(enosys());
+			},
+			mkdir(path, perm, callback) {
+				callback(enosys());
+			},
+			open(path, flags, mode, callback) {
+				callback(enosys());
+			},
+			read(fd, buffer, offset, length, position, callback) {
+				callback(enosys());
+			},
+			readdir(path, callback) {
+				callback(enosys());
+			},
+			readlink(path, callback) {
+				callback(enosys());
+			},
+			rename(from, to, callback) {
+				callback(enosys());
+			},
+			rmdir(path, callback) {
+				callback(enosys());
+			},
+			stat(path, callback) {
+				callback(enosys());
+			},
+			symlink(path, link, callback) {
+				callback(enosys());
+			},
+			truncate(path, length, callback) {
+				callback(enosys());
+			},
+			unlink(path, callback) {
+				callback(enosys());
+			},
+			utimes(path, atime, mtime, callback) {
+				callback(enosys());
+			},
+		};
+	}
+
+	if (!global.process) {
+		global.process = {
+			getuid() {
+				return -1;
+			},
+			getgid() {
+				return -1;
+			},
+			geteuid() {
+				return -1;
+			},
+			getegid() {
+				return -1;
+			},
+			getgroups() {
+				throw enosys();
+			},
+			pid: -1,
+			ppid: -1,
+			umask() {
+				throw enosys();
+			},
+			cwd() {
+				throw enosys();
+			},
+			chdir() {
+				throw enosys();
+			},
+		}
+	}
+
+	if (!global.crypto && global.require) {
+		const nodeCrypto = require("crypto");
+		global.crypto = {
+			getRandomValues(b) {
+				nodeCrypto.randomFillSync(b);
+			},
+		};
+	}
+	if (!global.crypto) {
+		throw new Error("global.crypto is not available, polyfill required (getRandomValues only)");
+	}
+
+	if (!global.performance) {
+		global.performance = {
+			now() {
+				const [sec, nsec] = process.hrtime();
+				return sec * 1000 + nsec / 1000000;
+			},
+		};
+	}
+
+	if (!global.TextEncoder && global.require) {
+		global.TextEncoder = require("util").TextEncoder;
+	}
+	if (!global.TextEncoder) {
+		throw new Error("global.TextEncoder is not available, polyfill required");
+	}
+
+	if (!global.TextDecoder && global.require) {
+		global.TextDecoder = require("util").TextDecoder;
+	}
+	if (!global.TextDecoder) {
+		throw new Error("global.TextDecoder is not available, polyfill required");
+	}
+
+
+	const isNodeJS = global.process && global.process.title === "node";
+
+	if (!isNodeJS) {
+		// console.log("ini browser fs")
+		// var myfs = global.BrowserFS.BFSRequire('fs');
+		// global.Buffer = global.BrowserFS.BFSRequire('buffer').Buffer;
+		// global.fs = myfs;
+
+		global.fs.constants = {
+			O_RDONLY: 0,
+			O_WRONLY: 1,
+			O_RDWR: 2,
+			O_CREAT: 64,
+			O_CREATE: 64,
+			O_EXCL: 128,
+			O_NOCTTY: 256,
+			O_TRUNC: 512,
+			O_APPEND: 1024,
+			O_DIRECTORY: 65536,
+			O_NOATIME: 262144,
+			O_NOFOLLOW: 131072,
+			O_SYNC: 1052672,
+			O_DIRECT: 16384,
+			O_NONBLOCK: 2048,
+		};
+
+		let outputBuf = "";
+
+		global.fs.writeSyncOriginal = global.fs.writeSync
+		global.fs.writeSync = function (fd, buf) {
+			if (fd === 1 || fd === 2) {
+				outputBuf += decoder.decode(buf);
+				const nl = outputBuf.lastIndexOf("\n");
+				if (nl != -1) {
+					console.log(outputBuf.substr(0, nl));
+					outputBuf = outputBuf.substr(nl + 1);
+				}
+				return buf.length;
+			} else {
+				return global.fs.writeSyncOriginal(...arguments);
+			}
+		};
+
+		global.fs.writeOriginal = global.fs.write
+		global.fs.write = function (fd, buf, offset, length, position, callback) {
+			// (corresponding to STDOUT/STDERR)
+			if (fd === 1 || fd === 2) {
+				if (offset !== 0 || length !== buf.length || position !== null) {
+					throw new Error("not implemented");
+				}
+				const n = this.writeSync(fd, buf);
+				callback(null, n, buf);
+			} else {
+				// buf: read buf first
+				arguments[1] = global.Buffer.from(arguments[1]);
+				return global.fs.writeOriginal(...arguments);
+			}
+		};
+
+
+
+		global.fs.openOriginal = global.fs.open
+		global.fs.open = function (path, flags, mode, callback) {
+			var myflags = 'r';
+			var O = global.fs.constants;
+
+			// Convert numeric flags to string flags
+			// FIXME: maybe wrong...
+			console.log("open dir?", path, 'flag', flags, myflags)
+			if (flags & O.O_WRONLY) { // 'w'
+				myflags = 'w';
+				if (flags & O.O_EXCL) {
+					myflags = 'wx';
+				}
+			} else if (flags & O.O_RDWR) { // 'r+' or 'w+'
+				if (flags & O.O_CREAT && flags & O.O_TRUNC) { // w+
+					if (flags & O.O_EXCL) {
+						myflags = 'wx+';
+					} else {
+						myflags = 'w+';
+					}
+				} else { // r+
+					myflags = 'r+';
+				}
+			} else if (flags & O.O_APPEND) { // 'a'
+				console.log("append error")
+				throw new Error("Not implmented");
+			} else {
+				// 打开文件
+				myflags = 'r+';
+				console.log("open dir?", path, 'flag', flags, myflags)
+			}
+
+
+			return global.fs.openOriginal(path, myflags, mode, callback);
+		};
+
+		global.fs.fstatOriginal = global.fs.fstat;
+		global.fs.fstat = function (fd, callback) {
+			return global.fs.fstatOriginal(fd, function () {
+				var retStat = arguments[1];
+				delete retStat['fileData'];
+				retStat.atimeMs = retStat.atime.getTime();
+				retStat.mtimeMs = retStat.mtime.getTime();
+				retStat.ctimeMs = retStat.ctime.getTime();
+				retStat.birthtimeMs = retStat.birthtime.getTime();
+				return callback(arguments[0], retStat);
+
+			});
+		};
+
+
+
+		global.fs.closeOriginal = global.fs.close;
+		global.fs.close = function (fd, callback) {
+			return global.fs.closeOriginal(fd, function () {
+				if (typeof arguments[0] === 'undefined') arguments[0] = null;
+				return callback(...arguments);
+			});
+		}
+
+		// global.fs.renameOriginal = global.fs.rename
+		// global.fs.rename = function (from, to, callback) {
+		// 	console.log("rename a0", arguments[0])
+		// 	global.fs.renameOriginal(from, to);
+		// 	callback(arguments[0])
+		// }
+
+		// global.fs.renameSyncOriginal = global.fs.renameSync
+		// global.fs.renameSync = function(fd, options) {
+		// 	console.log("Sync")
+		// }
+
+
+		global.fs = new Proxy(global.fs, handler);
+	}
+
+	// End of polyfills for common API.
+
+	const encoder = new TextEncoder("utf-8");
+	const decoder = new TextDecoder("utf-8");
+
+	global.Go = class {
+		constructor() {
+			this.argv = ["js"];
+			this.env = {};
+			this.exit = (code) => {
+				this.exitCode = code;
+				if (code !== 0) {
+					console.warn("exit code:", code);
+				}
+			};
+			this._exitPromise = new Promise((resolve) => {
+				this._resolveExitPromise = resolve;
+			});
+			this._pendingEvent = null;
+			this._scheduledTimeouts = new Map();
+			this._nextCallbackTimeoutID = 1;
+
+			const setInt64 = (addr, v) => {
+				this.mem.setUint32(addr + 0, v, true);
+				this.mem.setUint32(addr + 4, Math.floor(v / 4294967296), true);
+			}
+
+			const getInt64 = (addr) => {
+				const low = this.mem.getUint32(addr + 0, true);
+				const high = this.mem.getInt32(addr + 4, true);
+				return low + high * 4294967296;
+			}
+
+			const loadValue = (addr) => {
+				const f = this.mem.getFloat64(addr, true);
+				if (f === 0) {
+					return undefined;
+				}
+				if (!isNaN(f)) {
+					return f;
+				}
+
+				const id = this.mem.getUint32(addr, true);
+				return this._values[id];
+			}
+
+			const storeValue = (addr, v) => {
+				const nanHead = 0x7FF80000;
+
+				if (typeof v === "number" && v !== 0) {
+					if (isNaN(v)) {
+						this.mem.setUint32(addr + 4, nanHead, true);
+						this.mem.setUint32(addr, 0, true);
+						return;
+					}
+					this.mem.setFloat64(addr, v, true);
+					return;
+				}
+
+				if (v === undefined) {
+					this.mem.setFloat64(addr, 0, true);
+					return;
+				}
+
+				let id = this._ids.get(v);
+				if (id === undefined) {
+					id = this._idPool.pop();
+					if (id === undefined) {
+						id = this._values.length;
+					}
+					this._values[id] = v;
+					this._goRefCounts[id] = 0;
+					this._ids.set(v, id);
+				}
+				this._goRefCounts[id]++;
+				let typeFlag = 0;
+				switch (typeof v) {
+					case "object":
+						if (v !== null) {
+							typeFlag = 1;
+						}
+						break;
+					case "string":
+						typeFlag = 2;
+						break;
+					case "symbol":
+						typeFlag = 3;
+						break;
+					case "function":
+						typeFlag = 4;
+						break;
+				}
+				this.mem.setUint32(addr + 4, nanHead | typeFlag, true);
+				this.mem.setUint32(addr, id, true);
+			}
+
+			const loadSlice = (addr) => {
+				const array = getInt64(addr + 0);
+				const len = getInt64(addr + 8);
+				return new Uint8Array(this._inst.exports.mem.buffer, array, len);
+			}
+
+			const loadSliceOfValues = (addr) => {
+				const array = getInt64(addr + 0);
+				const len = getInt64(addr + 8);
+				const a = new Array(len);
+				for (let i = 0; i < len; i++) {
+					a[i] = loadValue(array + i * 8);
+				}
+				return a;
+			}
+
+			const loadString = (addr) => {
+				const saddr = getInt64(addr + 0);
+				const len = getInt64(addr + 8);
+				return decoder.decode(new DataView(this._inst.exports.mem.buffer, saddr, len));
+			}
+
+			const timeOrigin = Date.now() - performance.now();
+			this.importObject = {
+				go: {
+					// Go's SP does not change as long as no Go code is running. Some operations (e.g. calls, getters and setters)
+					// may synchronously trigger a Go event handler. This makes Go code get executed in the middle of the imported
+					// function. A goroutine can switch to a new stack if the current stack is too small (see morestack function).
+					// This changes the SP, thus we have to update the SP used by the imported function.
+
+					// func wasmExit(code int32)
+					"runtime.wasmExit": (sp) => {
+						sp >>>= 0;
+						const code = this.mem.getInt32(sp + 8, true);
+						this.exited = true;
+						delete this._inst;
+						delete this._values;
+						delete this._goRefCounts;
+						delete this._ids;
+						delete this._idPool;
+						this.exit(code);
+					},
+
+					// func wasmWrite(fd uintptr, p unsafe.Pointer, n int32)
+					"runtime.wasmWrite": (sp) => {
+						sp >>>= 0;
+						const fd = getInt64(sp + 8);
+						const p = getInt64(sp + 16);
+						const n = this.mem.getInt32(sp + 24, true);
+						fs.writeSync(fd, new Uint8Array(this._inst.exports.mem.buffer, p, n));
+					},
+
+					// func resetMemoryDataView()
+					"runtime.resetMemoryDataView": (sp) => {
+						sp >>>= 0;
+						this.mem = new DataView(this._inst.exports.mem.buffer);
+					},
+
+					// func nanotime1() int64
+					"runtime.nanotime1": (sp) => {
+						sp >>>= 0;
+						setInt64(sp + 8, (timeOrigin + performance.now()) * 1000000);
+					},
+
+					// func walltime1() (sec int64, nsec int32)
+					"runtime.walltime1": (sp) => {
+						sp >>>= 0;
+						const msec = (new Date).getTime();
+						setInt64(sp + 8, msec / 1000);
+						this.mem.setInt32(sp + 16, (msec % 1000) * 1000000, true);
+					},
+
+					// func scheduleTimeoutEvent(delay int64) int32
+					"runtime.scheduleTimeoutEvent": (sp) => {
+						sp >>>= 0;
+						const id = this._nextCallbackTimeoutID;
+						this._nextCallbackTimeoutID++;
+						this._scheduledTimeouts.set(id, setTimeout(
+							() => {
+								this._resume();
+								while (this._scheduledTimeouts.has(id)) {
+									// for some reason Go failed to register the timeout event, log and try again
+									// (temporary workaround for https://github.com/golang/go/issues/28975)
+									console.warn("scheduleTimeoutEvent: missed timeout event");
+									this._resume();
+								}
+							},
+							getInt64(sp + 8) + 1, // setTimeout has been seen to fire up to 1 millisecond early
+						));
+						this.mem.setInt32(sp + 16, id, true);
+					},
+
+					// func clearTimeoutEvent(id int32)
+					"runtime.clearTimeoutEvent": (sp) => {
+						sp >>>= 0;
+						const id = this.mem.getInt32(sp + 8, true);
+						clearTimeout(this._scheduledTimeouts.get(id));
+						this._scheduledTimeouts.delete(id);
+					},
+
+					// func getRandomData(r []byte)
+					"runtime.getRandomData": (sp) => {
+						sp >>>= 0;
+						crypto.getRandomValues(loadSlice(sp + 8));
+					},
+
+					// func finalizeRef(v ref)
+					"syscall/js.finalizeRef": (sp) => {
+						sp >>>= 0;
+						const id = this.mem.getUint32(sp + 8, true);
+						this._goRefCounts[id]--;
+						if (this._goRefCounts[id] === 0) {
+							const v = this._values[id];
+							this._values[id] = null;
+							this._ids.delete(v);
+							this._idPool.push(id);
+						}
+					},
+
+					// func stringVal(value string) ref
+					"syscall/js.stringVal": (sp) => {
+						sp >>>= 0;
+						storeValue(sp + 24, loadString(sp + 8));
+					},
+
+					// func valueGet(v ref, p string) ref
+					"syscall/js.valueGet": (sp) => {
+						sp >>>= 0;
+						const result = Reflect.get(loadValue(sp + 8), loadString(sp + 16));
+						sp = this._inst.exports.getsp() >>> 0; // see comment above
+						storeValue(sp + 32, result);
+					},
+
+					// func valueSet(v ref, p string, x ref)
+					"syscall/js.valueSet": (sp) => {
+						sp >>>= 0;
+						Reflect.set(loadValue(sp + 8), loadString(sp + 16), loadValue(sp + 32));
+					},
+
+					// func valueDelete(v ref, p string)
+					"syscall/js.valueDelete": (sp) => {
+						sp >>>= 0;
+						Reflect.deleteProperty(loadValue(sp + 8), loadString(sp + 16));
+					},
+
+					// func valueIndex(v ref, i int) ref
+					"syscall/js.valueIndex": (sp) => {
+						sp >>>= 0;
+						storeValue(sp + 24, Reflect.get(loadValue(sp + 8), getInt64(sp + 16)));
+					},
+
+					// valueSetIndex(v ref, i int, x ref)
+					"syscall/js.valueSetIndex": (sp) => {
+						sp >>>= 0;
+						Reflect.set(loadValue(sp + 8), getInt64(sp + 16), loadValue(sp + 24));
+					},
+
+					// func valueCall(v ref, m string, args []ref) (ref, bool)
+					"syscall/js.valueCall": (sp) => {
+						sp >>>= 0;
+						try {
+							const v = loadValue(sp + 8);
+							const m = Reflect.get(v, loadString(sp + 16));
+							const args = loadSliceOfValues(sp + 32);
+							const result = Reflect.apply(m, v, args);
+							sp = this._inst.exports.getsp() >>> 0; // see comment above
+							storeValue(sp + 56, result);
+							this.mem.setUint8(sp + 64, 1);
+						} catch (err) {
+							storeValue(sp + 56, err);
+							this.mem.setUint8(sp + 64, 0);
+						}
+					},
+
+					// func valueInvoke(v ref, args []ref) (ref, bool)
+					"syscall/js.valueInvoke": (sp) => {
+						sp >>>= 0;
+						try {
+							const v = loadValue(sp + 8);
+							const args = loadSliceOfValues(sp + 16);
+							const result = Reflect.apply(v, undefined, args);
+							sp = this._inst.exports.getsp() >>> 0; // see comment above
+							storeValue(sp + 40, result);
+							this.mem.setUint8(sp + 48, 1);
+						} catch (err) {
+							storeValue(sp + 40, err);
+							this.mem.setUint8(sp + 48, 0);
+						}
+					},
+
+					// func valueNew(v ref, args []ref) (ref, bool)
+					"syscall/js.valueNew": (sp) => {
+						sp >>>= 0;
+						try {
+							const v = loadValue(sp + 8);
+							const args = loadSliceOfValues(sp + 16);
+							const result = Reflect.construct(v, args);
+							sp = this._inst.exports.getsp() >>> 0; // see comment above
+							storeValue(sp + 40, result);
+							this.mem.setUint8(sp + 48, 1);
+						} catch (err) {
+							storeValue(sp + 40, err);
+							this.mem.setUint8(sp + 48, 0);
+						}
+					},
+
+					// func valueLength(v ref) int
+					"syscall/js.valueLength": (sp) => {
+						sp >>>= 0;
+						setInt64(sp + 16, parseInt(loadValue(sp + 8).length));
+					},
+
+					// valuePrepareString(v ref) (ref, int)
+					"syscall/js.valuePrepareString": (sp) => {
+						sp >>>= 0;
+						const str = encoder.encode(String(loadValue(sp + 8)));
+						storeValue(sp + 16, str);
+						setInt64(sp + 24, str.length);
+					},
+
+					// valueLoadString(v ref, b []byte)
+					"syscall/js.valueLoadString": (sp) => {
+						sp >>>= 0;
+						const str = loadValue(sp + 8);
+						loadSlice(sp + 16).set(str);
+					},
+
+					// func valueInstanceOf(v ref, t ref) bool
+					"syscall/js.valueInstanceOf": (sp) => {
+						sp >>>= 0;
+						this.mem.setUint8(sp + 24, (loadValue(sp + 8) instanceof loadValue(sp + 16)) ? 1 : 0);
+					},
+
+					// func copyBytesToGo(dst []byte, src ref) (int, bool)
+					"syscall/js.copyBytesToGo": (sp) => {
+						sp >>>= 0;
+						const dst = loadSlice(sp + 8);
+						const src = loadValue(sp + 32);
+						if (!(src instanceof Uint8Array || src instanceof Uint8ClampedArray)) {
+							this.mem.setUint8(sp + 48, 0);
+							return;
+						}
+						const toCopy = src.subarray(0, dst.length);
+						dst.set(toCopy);
+						setInt64(sp + 40, toCopy.length);
+						this.mem.setUint8(sp + 48, 1);
+					},
+
+					// func copyBytesToJS(dst ref, src []byte) (int, bool)
+					"syscall/js.copyBytesToJS": (sp) => {
+						sp >>>= 0;
+						const dst = loadValue(sp + 8);
+						const src = loadSlice(sp + 16);
+						if (!(dst instanceof Uint8Array || dst instanceof Uint8ClampedArray)) {
+							this.mem.setUint8(sp + 48, 0);
+							return;
+						}
+						const toCopy = src.subarray(0, dst.length);
+						dst.set(toCopy);
+						setInt64(sp + 40, toCopy.length);
+						this.mem.setUint8(sp + 48, 1);
+					},
+
+					"debug": (value) => {
+						console.log(value);
+					},
+				}
+			};
+		}
+
+		async run(instance) {
+			if (!(instance instanceof WebAssembly.Instance)) {
+				throw new Error("Go.run: WebAssembly.Instance expected");
+			}
+			this._inst = instance;
+			this.mem = new DataView(this._inst.exports.mem.buffer);
+			this._values = [ // JS values that Go currently has references to, indexed by reference id
+				NaN,
+				0,
+				null,
+				true,
+				false,
+				global,
+				this,
+			];
+			this._goRefCounts = new Array(this._values.length).fill(Infinity); // number of references that Go has to a JS value, indexed by reference id
+			this._ids = new Map([ // mapping from JS values to reference ids
+				[0, 1],
+				[null, 2],
+				[true, 3],
+				[false, 4],
+				[global, 5],
+				[this, 6],
+			]);
+			this._idPool = []; // unused ids that have been garbage collected
+			this.exited = false; // whether the Go program has exited
+
+			// Pass command line arguments and environment variables to WebAssembly by writing them to the linear memory.
+			let offset = 4096;
+
+			const strPtr = (str) => {
+				const ptr = offset;
+				const bytes = encoder.encode(str + "\0");
+				new Uint8Array(this.mem.buffer, offset, bytes.length).set(bytes);
+				offset += bytes.length;
+				if (offset % 8 !== 0) {
+					offset += 8 - (offset % 8);
+				}
+				return ptr;
+			};
+
+			const argc = this.argv.length;
+
+			const argvPtrs = [];
+			this.argv.forEach((arg) => {
+				argvPtrs.push(strPtr(arg));
+			});
+			argvPtrs.push(0);
+
+			const keys = Object.keys(this.env).sort();
+			keys.forEach((key) => {
+				argvPtrs.push(strPtr(`${key}=${this.env[key]}`));
+			});
+			argvPtrs.push(0);
+
+			const argv = offset;
+			argvPtrs.forEach((ptr) => {
+				this.mem.setUint32(offset, ptr, true);
+				this.mem.setUint32(offset + 4, 0, true);
+				offset += 8;
+			});
+
+			this._inst.exports.run(argc, argv);
+			if (this.exited) {
+				this._resolveExitPromise();
+			}
+			await this._exitPromise;
+		}
+
+		_resume() {
+			if (this.exited) {
+				throw new Error("Go program has already exited");
+			}
+			this._inst.exports.resume();
+			if (this.exited) {
+				this._resolveExitPromise();
+			}
+		}
+
+		_makeFuncWrapper(id) {
+			const go = this;
+			return function () {
+				const event = {
+					id: id,
+					this: this,
+					args: arguments
+				};
+				go._pendingEvent = event;
+				go._resume();
+				return event.result;
+			};
+		}
+	}
+
+	if (
+		typeof module !== "undefined" &&
+		global.require &&
+		global.require.main === module &&
+		global.process &&
+		global.process.versions &&
+		!global.process.versions.electron
+	) {
+		if (process.argv.length < 3) {
+			console.error("usage: go_js_wasm_exec [wasm binary] [arguments]");
+			process.exit(1);
+		}
+
+		const go = new Go();
+		go.argv = process.argv.slice(2);
+		go.env = Object.assign({
+			TMPDIR: require("os").tmpdir()
+		}, process.env);
+		go.exit = process.exit;
+		WebAssembly.instantiate(fs.readFileSync(process.argv[2]), go.importObject).then((result) => {
+			process.on("exit", (code) => { // Node.js exits if no event handler is pending
+				if (code === 0 && !go.exited) {
+					// deadlock, make Go print error and stack traces
+					go._pendingEvent = {
+						id: 0
+					};
+					go._resume();
+				}
+			});
+			return go.run(result.instance);
+		}).catch((err) => {
+			console.error(err);
+			process.exit(1);
+		});
+	}
+})();